There is currently an emerging consumer market for certain types of wearable peripheral devices that are used as companion products to smartphone devices. Their popularity can be traced, in part, to the variety of features they offer. Such devices include, for example, rings, necklaces, glasses, and “wristlets” (e.g., a watch or wristband) that is worn around a user's wrist.
One feature provided by these wearable devices allows the wearable devices to be used as a personal token to automatically gain access to a smartphone that is in a locked state. Particularly, a wearable device worn by the user may communicate a code or token to the user's smartphone, thereby permitting the user to bypass the manual entry of a predetermined unlock sequence associated with the smartphone. However, this feature works best when the wireless communications device and the wearable device are physically very close to each other. One way to measure a distance between the two devices is to measure the signal strength of the wearable device when it transmits at a standard power.
Such methods, however, are problematic. For example, it is difficult to determine based on the measurements whether a peripheral device is very close to a wireless communications device with a clear line of sight, or whether there are objects disposed between the devices that block or deflect transmissions from the wearable device. Further, signals transmitted by the wearable device may be reflected or deflected by different objects even when there is a clear line of sight between the two devices. Thus, such measurements may not be able to accurately determine whether the wearable device is sufficiently close to the wireless communications device.